This invention relates generally to cargo bars that are used to restrain freight in truck bodies and other vehicles. More particularly, the invention is directed to a cargo bar which is constructed so that it can be easily released and also to prevent excessive force from being applied by the bar.
Freight vehicles such as over the road trailers and smaller trucks commonly use cargo bars which hold boxes and other freight containers in place. The cargo bar extends across the truck body between the opposite side walls and in some cases vertically between the floor and ceiling. It is placed where it acts as a barrier that prevents the cargo from shifting due to sudden starts and stops or other forces that may be encountered in transit.
In order to function effectively, the cargo bar must be wedged tightly in place so that it can withstand the forces that are exerted by the cargo. One commonly used type of cargo bar is constructed with pads on opposite ends of the bar which bear against the vehicle walls (or the floor and ceiling). A jack or ratchet mechanism operated by a reciprocating handle extends the bar to tightly secure it in place in extension between the walls or between the floor and ceiling. In a typical ratchet mechanism, one set of pawls advance the bar when the handle is reciprocated and another set of pawls hold the bar and prevent it from retracting before the next stroke is effected.
One of the principal problems with this type of cargo bar is that it is difficult to release. The bar is often necessarily tightened to the point where it exerts up to 300 pounds or even more to function adequately. In order to release the bar to permit the cargo to be unloaded, this force must be overcome with a greater force applied to the holding pawls. Often, a hammer or the like must be forcefully struck against the holding pawl to release them. This can cause injury to workers and damage to the pawls or other equipment and is burdensome in any event.
Another problem is that the ratchet can be operated so aggressively that it applies excessive force to the trailer walls. The walls can be bent or otherwise permanently damaged by the bar if this occurs. Although measures have been taken in the past to limit the force that can be exerted by the cargo bar, using hydraulic pressure relief or mechanical techniques, there is ample room for improvement to reduce the cost, complexity and reliability of the force limitation system.
The present invention is directed to a cargo bar in which the holding pawls are easily released and in which the force that can be applied by the bar is limited.
More particularly, it is an object of the invention to provide a cargo bar that is specially constructed to make use of the leverage of the ratchet handle for release of the holding pawls. In this regard, the ratchet head is pivoted to the ratchet housing through a slotted opening which allows the ratchet to be operated normally. When the cargo bar needs to be released, the slotted opening allows the ratchet head to be shifted to a release position where a strategically located angled surface of the ratchet head acts in camming fashion to release the holding pawls when the ratchet handle is further operated to pivot the ratchet head beyond its normal operating range.
Another important feature of the invention is an improved mechanism for limiting the force that can be applied by the cargo bar. This is accomplished by a spring loaded tubular collar which is mounted such that it progressively moves toward the holding pawls as the cargo bar is extended to exert increasing force. The spring which acts against the collar is selected so that it is compressed to exert the maximum allowable force (300 pounds, for example) at the point where the collar is butted up against the holding pawls. Thereafter, the collar provides a mechanical stop that prevents the ratchet head from pivoting in the area between the advancement pawls and the holding pawls. As a result, the ratchet can no longer be operated and the cargo bar cannot be extended beyond the length at which it applies the maximum allowable force.
Among the other objects of the invention are to provide a cargo bar of the character described which has a rugged construction, which is simple and economical to manufacture, and which functions reliably over an extended operating life.
Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description.